High Mercury Levels Found in Idaho, Nev. Fish

Fish tissue samples taken from rainbow trout collected from four Idaho and Nevada reservoirs revealed elevated concentrations of methylmercury, according to data released by the U.S. Geological Survey (USGS) and the Shoshone-Paiute Tribes of the Duck Valley Indian Reservation.

The Tribes and USGS collaborated on and jointly funded the study. The tissue samples were analyzed at the USGS Mercury Research Laboratory in Middleton, WI.

"The concentrations found were generally elevated for rainbow trout," said Terry Maret, the USGS scientist who directed the sampling. Maret referred to a study conducted by the U.S. Environmental Protection Agency, which found that the average mercury concentration in rainbow trout across the United States was about 0.11 parts per million (ppm), wet weight. "About 70 percent of the fish filets analyzed were above this," he said.

Three of the four sample sites are located on the Duck Valley Indian Reservation, which spans the border between southwestern Idaho and northeastern Nevada. At the Tribes' request, public health toxicologists from the Idaho Department of Health and Welfare reviewed the USGS lab data for fish collected from those three reservoirs and recommended that the Tribes establish the following fish consumption guidelines:

  1. Up to two meals per month of fish taken from Mountain View Reservoir and Lake Billy Shaw, and up to five meals per month of fish taken from Sheep Creek Reservoir can be consumed safely by children and pregnant women.

  2. Up to eight meals per month of fish taken from Mountain View Reservoir and Lake Billy Shaw, and up to 20 meals per month of fish taken from Sheep Creek Reservoir can be consumed safely by the general public other than children and pregnant women.

The meal size is four ounces for children and eight ounces for adults. The toxicologists emphasized that rainbow trout from the reservation reservoirs remain a healthy food choice within the recommended consumption guidelines.

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